The present invention relates to a liquid crystal display device and a manufacturing method thereof, and more particularly to a technique which is effectively applicable to a method for manufacturing a liquid crystal display panel by multiple-piece simultaneous manufacturing.
An active-matrix-type TFT liquid crystal display device (hereinafter simply referred to as liquid crystal display device) has been popularly used as a liquid crystal display for a liquid crystal television receiver set or a personal computer, or a liquid crystal display of a portable electronic device such as a mobile phone terminal.
The liquid crystal display device includes a liquid crystal display panel where a liquid crystal material is sealed between a pair of substrates, and a display region of a liquid crystal display panel is constituted of a mass of pixels each of which has a TFT element, a pixel electrode, a common electrode and a liquid crystal layer (liquid crystal material). Further, in case of the active-matrix-type liquid crystal display device, the liquid crystal display panel includes a plurality of scanning signal lines and a plurality of video signal lines.
Here, the TFT element of each pixel has a source thereof connected to the pixel electrode and a drain thereof connected to one of the plurality of video signal lines. Further, the TFT element of each pixel has a gate electrode thereof connected to one of the plurality of scanning signal lines.
In the liquid crystal display device, a video or an image is displayed by controlling a transmission quantity of light in each pixel, a reflection quantity of light or both the transmission quantity and the reflection quantity of light based on a potential difference between the pixel electrode and the common electrode. Here, in the liquid crystal display device, an operation in which a plurality of TFT elements each of which has a gate electrode thereof connected to one scanning signal line out of a plurality of scanning signal lines are turned on, and a video signal (grayscale voltage) which is applied to the respective video signal lines is written in the pixel electrodes via the TFT elements is repeatedly performed.
Here, also in the liquid crystal display device, the video or an image is displayed by inverting polarity of each pixel for every preset frame period, that is, by inverting the level relationship between a potential of the pixel electrode and a potential of the common electrode.
In the conventional liquid crystal display device, for example, image retention attributed to distortions (rounding) of a waveform of a scanning signal applied to the scanning signal line is liable to occur. It is known that the image retention attributed to distortions of the waveform of the scanning signal is liable to occur at a portion of the scanning signal line remote from a signal input end in general. As a method for reducing such image retention attributed to the distortions of the waveform of the scanning signal, for example, there has been proposed a method which increases parasitic capacitance Cgs formed between a gate electrode and a source electrode of a TFT element corresponding to the increase of a distance from a signal input end of a scanning signal line (see JP-A-2004-093821 (patent document 1), for example).